Kentucky state officials yesterday told families of miners killed in an explosion that a wall intended to seal off a closed section of the mine was improperly built and that the federal Mine Safety and Health Administration refused to let them question one of its inspectors about the case.

The report by a team from the Kentucky Office of Mine Safety and Licensing is to be released at noon today. It says the miners died when a cutting torch one of them was using ignited methane that had built up behind a wall erected to close an abandoned section of the mine, located in Harlan County.

Killed were Amon Brock, 51; Jimmy Lee, 33; Roy Middleton, 35; Bill Petra, 49 and Paris Thomas, 53. Two of the men -- Mr. Brock and Mr. Lee -- died in the May 20 explosion. Three others died of carbon monoxide poisoning when the blast consumed usable air inside the mine.

The mine was closed after the explosion and has not reopened.

The investigation found that Mr. Brock and Mr. Lee were cutting a set of metal straps above the wall. The straps make up a lattice-like metal frame that buttresses the mine roof.

The straps, which were capable of carrying an electrical charge from the working side of the mine to the closed off area, were a matter of concern because of an explosion five months earlier at the Sago Mine in Upshur County, W.Va. In that accident investigators had theorized that a lightning strike somehow triggered a methane blast that claimed the lives of 12 men.

As in the case of Sago, the wall at the Darby mine was built of lightweight Omega Block, a foam-and-cement material favored by mine operators because of its light weight.

The Kentucky investigators discovered that the Omega Block wall at Darby had been stacked dry, without mortar between the joints, and that the mine construction crew had failed to build the wall into notches in the mine floor and walls as required by MSHA.

The report states that one of the miners, Mr. Brock, indicated that he needed to remove the metal straps on the mine roof above the wall and invited Mr. Lee, who was ending his shift, to come along.

"Brock told Jimmy Lee that the job they were going to stay late and do would only take 10 or 15 minutes. After hearing this, Jimmy Lee decided to work late with Amon Brock," the report says.

James Philpot, a Kentucky Darby miner who was interviewed by a joint state-federal panel, "told investigators that Amon Brock had to get something done because a federal mine inspector Stanley Sturgill would be back at the mine on Monday."

Mr. Sturgill's role, and whether he instructed mine officials to remove the straps, was unclear. State investigators said they were not permitted to question Mr. Sturgill.

A lawyer for the families of three of the victims, Tony Oppegard, last night said he was also not permitted to question Mr. Sturgill. Mr. Oppegard said federal investigators did not ask Mr. Sturgill about why the men were cutting the straps.

Kentucky state officials made a formal request to MSHA to allow inspector Stanley Sturgill to be interviewed by OMSL's investigation team," the report says. "In addition OMSL requested copies of Mr. Sturgill's notes and transcripts of the MSHA formal interviews that had been done by MSHA. MSHA verbally declined the request for an interview but advised the state that Sturgill would reply to a written set of questions."

The report said that state investigators have not yet received a reply to those written questions.

"There's only two possible explanations for why they were cutting these straps," Mr. Oppegard said last night. "Number one is that they were told to do that by an MSHA inspector, or for some reason the company thought the straps were a violation and they had to get them down before the inspector came back on Monday.

The report also said the men should not have been using an acetylene torch to cut the roof straps.

Mr. Oppegard also last night said portions of the report that indicate that all of the victims had used only part of the fuel in their self-contained self-rescue breathing devices suggests the units failed to work properly.

Dirk Fillpot, a spokesman for MSHA, said the agency will be issuing its own report on the accident at a later date.